The goal of this project is to understand the neural mechanisms of the basal ganglia that mediate sequences of behavior. Motor disorders of the basal ganglia, such as Parkinson's and Huntington's disease, are associated with a profound loss of the ability to organize and execute sequences of movement. Furthermore, cognitive disorders of the basal ganglia such as Tourette's syndrome and obesessive compulsive disorder suggest that sequential control mechanisms may be a fundamental property of the basal ganglia. In this project, single neuron activity in the basal ganglia will be related to instinctive and learned behavior sequences to understand basal ganglia coordination of sequences, and to identify basic principles for sequential organization. Additional goals are to determine whether there are different neuronal substrates for learned and instinctive sequences and to determine the computational properties of sequence-related neuronal assemblies in the basal ganglia. A key hypothesis to be tested is that neuronal activity in the basal ganglia will be related to movements within the context of grooming sequences, and not related to these movements when they occur outside of these sequences. Single neurons will be recorded in rats during stereotyped sequential grooming and when components of movements are made in isolation or in other sequential patterns. Lastly, experiments will test the hypothesis that neostriatal neurons mediate sequences by modulating sensorimotor responsiveness. For those experiments, neuronal activity will be recorded after lesions of the substantia nigra, which disrupt sequential grooming, or by presenting cutaneous and taste stimuli during sequence execution.